I built this but didn't end up making it so buyer beware - you may need to tweak a little.
The two holes for mounting the stock conical mount are made for M3 machine screws. One side has a recess for an M3 threaded insert. The other side has a recess for a M3 nut.
Use wood screws or similar to attach to your wall or ceiling.
The author marked this model as their own original creation.